filter out unconnected pseudo nodes on the outside

The change is necessitated by the removal of procspied/ebpf endpoint
filtering in the renderers, as a result of which the odd
conntracked-only, unconnected pseudo node can sneak through.

This new way of doing things also makes renderers more composable and
robust, and more directly reflects the objective:
- in the process topologies, filter out all unconnected nodes
- in all other topologies, filter out unconnected pseudo nodes

render/container.go

@@ -68,13 +68,13 @@ func ConnectionJoin(r Renderer, toIPs func(report.Node) []string) Renderer {
 		return result
 	}
 
-	return FilterUnconnected(MakeMap(
+	return MakeMap(
 		ipToNode,
 		MakeReduce(
 			MakeMap(nodeToIP, r),
 			mapEndpoint2IP,
 		),
-	))
+	)
 }
 
 func ipToNode(n report.Node, _ report.Networks) report.Nodes {

render/filters.go

@@ -215,7 +215,7 @@ func Complement(f FilterFunc) FilterFunc {
 // FilterUnconnected produces a renderer that filters unconnected nodes
 // from the given renderer
 func FilterUnconnected(r Renderer) Renderer {
-	return MakeFilter(
+	return MakeFilterPseudo(
 		func(node report.Node) bool {
 			_, ok := node.Latest.Lookup(IsConnected)
 			return ok
@@ -224,6 +224,21 @@ func FilterUnconnected(r Renderer) Renderer {
 	)
 }
 
+// FilterUnconnectedPseudo produces a renderer that filters
+// unconnected pseudo nodes from the given renderer
+func FilterUnconnectedPseudo(r Renderer) Renderer {
+	return MakeFilterPseudo(
+		func(node report.Node) bool {
+			if !IsPseudoTopology(node) {
+				return true
+			}
+			_, ok := node.Latest.Lookup(IsConnected)
+			return ok
+		},
+		ColorConnected(r),
+	)
+}
+
 // Noop allows all nodes through
 func Noop(_ report.Node) bool { return true }